The fenestration industry dates from antiquity and mankind has used many methods of securing the openings in buildings that provide light, air and access. After the invention of steel and the methods of readily producing clear glass were developed it became commonplace to enclose openings by means of slender steel framework that held glass panels by means of clips and glazing putty. This allowed for a higher level of shelter to be constructed. Windows made from steel and glass allowed natural light while providing protection from the elements and this paved the way to control indoor temperature. The invention of air conditioning induced a further need to control air infiltration, radiant energy and thermal transfer and consequently steel window production slowly gave way to more energy efficient methods of construction. This transition significantly altered the architectural style that had been established with the low profile steel windows. The applicants present invention allows for the architectural style established with the narrow sight lines of steel windows with a maintenance free window that has the thermal performance required in modern construction.